Figure 4.

Phylogenetic tree based on 16S rRNA gene sequences showing the position of Pyrobaculum calidifontis (strain VA1). Multiple sequence alignments were performed with ClustalW. Tree topology and evolutionary distance estimations were performed by the neighbor-joining method. Scale bar indicates 10 substitutions per 100 nucleotides. Numbers represent bootstrap probabilities (%). The accession numbers are as follows: Acidianus infernus, D85505; Aeropyrum pernix, AB008745; Aquifex pyrophilus, M83548; Archaeoglobus fulgidus, Y00275; Desulfurococcus mobilis, M36474; Methanococcus vannielii, M36507; Methanopyrus kandleri, M59932; Methanothermus fervidus, M59145; Pyrobaculum aerophilum, L07510; Pyrobaculum arsenaticum, AJ277124; Pyrobaculum calidifontis, AB078332; Pyrobaculum islandicum, L07511; Pyrobaculum oguniense, AB029339; Pyrococcus furiosus, U20163; Pyrodictium occultum, M21087; Pyrolobus fumarii, X99555; Sulfolobus acidocaldarius, D14876; Thermococcus kodakaraensis, D38650; Thermofilum pendens, X14835; Thermoproteus neutrophilus, AB009618; Thermoproteus tenax, M35966; and Thermotoga maritima, M21774.